Biological drugs such as protein or polypeptide drugs, especially oral insulin preparation have been being the subject matter sought to be solved in pharmaceutical field. This is because biological drugs such as insulin by oral administration can not usually be absorbed and the bio-availability thereof is low. At present, biological drugs such as insulin are mainly administrated to patients by injection, which makes patients inconvenient and painful. Therefore, it is necessary to develop protein or polypeptide drugs such as insulin oral preparation.
U.S. Pat. No. 5,840,332 discloses a gastrointestinal delivery system, which comprises a drug in combination with a core material, the core being surrounded by a water-insoluble or relatively water-insoluble coating material, the core material includes calcium pectinate containing 2-4% calcium by weight (see column 15 line 4), gastrointestinal tract includes colon, and the drug contains protein or polypeptide drug such as insulin. However, the prior art does not provide any a specific solution of carrying out release of oral preparation of protein or polypeptide drugs in colon. In addition, it was reported that a proteinase inhibitor as an absorption promoter was used to improve the bio-availability of insulin oral preparation, but the bio-availability of insulin oral preparation obtained is merely 5.73-7.58%, which can not satisfy clinical requirements, and simultaneously long-term use of the proteinase inhibitor may cause the disturbance of gastrointestinal function.